During vascular surgery or endovascular treatment of vessels including atherectomy, balloon angioplasty, and/or stent deployment, debris such as plaque and blood clots can move from the treatment site through a vein or artery, thus compromising the flow of blood at a location distal from the treatment site. Various distal protection systems have been developed to prevent such debris from embolizing in the vessel. Such distal protection devices include filters and occlusive devices, (e.g., balloons) placed distally of the treatment site.
It is desirable to place a distal protection device at a chosen location in order to achieve good sealing between the device and the wall of the vessel. Frequently it is necessary to match the protection device diameter with the vessel diameter, and vessels are known to taper or to have diameters that vary due to disease. It is also desirable to place the protection device in a relatively disease free portion of the vessel so as to minimize liberation of emboli from the wall of the vessel due to interaction with the protection device. Further, it is desirable that the device remains at the desired location during the procedure.
Distal protection devices typically are mounted on a wire or tube that functions as a guidewire. The distal protection devices are either fixedly attached to the guidewire or attached so as to permit a limited amount of motion between the device and the guidewire. Frequently, the same guidewire used to carry the device is also used to guide various catheters to and from the treatment site. For example, during the procedure, catheters may be exchanged over this guidewire.
The wire or tube comprising the guidewire typically passes through or alongside the filter and terminates in an atraumatic tip. This arrangement helps assure correct deployment of the distal protection device. A disadvantage to this, however, is that a continuous wire or tube has a stiffness that can cause vessel damage. Inadvertent axial motion of the wire or tube can also dislodge emboli. Because the wire or tube is stiff, the vessel within which it resides can be forced to take on its shape and become straightened. This is undesirable as this stresses the vessel. Further, the wire can press against the protection device disrupting the apposition of the device to the vessel. This can result not only in damage to the vessel but in dissection of the vessel. In addition, a stiff wire or tube, while desirable in controlling placement of a distal protection device, can prevent navigation of the device through tortuous anatomy.
Many distal protection devices such as the one shown in FIGS. 1A and B utilize a filter having a distal end that slides over or along an elongate support member SM such as a guidewire. The filter F is shown in its expanded deployed configuration in FIG. 1A and in its contracted delivery configuration in FIG. 1B. In these devices the distal end is at a first position with respect to the elongate support member when the filter is in its contracted delivery configuration and at a second more proximal position when the filter is in its expanded deployed configuration. In these designs, the length of the elongate support member that extends distally of the distal end of the filter must be increased by an amount S equal to the distance between the first and second positions to accommodate the slideable distal end of the filter. This increased elongate support member length distal to the filter can be a disadvantage for the reasons set forth above. In addition, this increased elongate support member length can prevent the filter from being used in connection with the treatment of distal lesions in the vascular anatomy since placement of the filter at a location distal to the treatment site may not be possible.
Thus, there is need in the art for a distal protection device that would avoid vessel damage and excessive vessel straightening while at the same time providing for distal vessel placement and superior navigation through tortuous anatomy.